1. Field of the Invention
The present invention relates to a method for recording information on an optical disc and a device for recording information on an optical disc. Further, the present invention relates to an optical disc on which information is recorded by such a recording method, and to a method for manufacturing such an optical disc. Furthermore, the present invention relates to an optical disc drive device for reading out information from such an optical disc.
2. Description of the Related Art
There are widely used optical discs such as Blu-ray discs (BD), digital versatile disks (DVD), and compact disks (CD). These optical discs can be used as, e.g., a boot disk. The boot disk refers to an optical disc on which information (hereinafter, referred to as “boot information”) is recorded to which a computer refers for booting an operating system (hereinafter, abbreviated as “OS”). Examples of elements of the boot information encompass programs such as a kernel and a device driver and data to which these programs refer.
The optical disc is superior in portability to a hard disk housed in a computer. Therefore, the use of an optical disc on which the boot information is recorded makes it possible to cause a same OS to operate both on a computer in a home and on a computer outside the home. In addition, the optical disc on which the boot information is recorded can be used in booting a computer whose internal hard disk has a failure.
However, a seek speed of the optical disc is lower than that of the hard disk drive. That is, a speed for random access to the optical disc is lower than a speed for random access to the hard disk. For this reason, a time required for booting the OS from the optical disc is longer, than a time required for booting the OS from the hard disk. Further, in a case where a process to be carried out after the OS is booted involves access to the optical disc, a time required for the process is also longer than that required for the process involving no access to the optical disc.
Actually, an optical disc to be used as a boot disk generally stores an accessory tool, data, preinstalled application software, etc., in addition to the boot information. Areas where the boot information is recorded are discretely arranged. Therefore, for example, it takes 10 minutes to 15 minutes to boot an OS by reading out, from a Blu-ray disc, boot information of approximately 300 MB to 400 MB.
Techniques for shortening a time required for booting an OS from a disc are described in, e.g., Patent Literature 1 and Non-Patent Literatures 1 and 2. Patent Literature 1 discloses a technique by which a time required for booting an OS is shortened by copying, in a main memory in advance, content of a specific file recorded on a disk. Non-Patent Literatures 1 and 2 disclose a technique for increasing a speed of an OS boot process that utilizes a compressed loop device (cloop) stored on an optical disc. Specifically, the speed is increased by optimizing positions of compressed blocks constituting the compressed loop device.
Techniques for increasing a speed of random disc access encompass, e.g., an art disclosed in Patent Literature 2. Patent Literature 2 discloses a technique by which a random access speed is increased in such a manner that a disk array apparatus housing a plurality of hard disk drives relocates data on the basis of past access history.